1991 Pontiac Grand Prix Problems

RepairPal has identified the most common problems with the 1991 Pontiac Grand Prix as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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Known Problems

The high pressure power steering hose will commonly leak fluid; it should be replaced.

The intake manifold gasket may develop and external engine oil or coolant leak. In some cases, an internal coolant leak may occur causing coolant to mix with the engine oil. Our technicians tell us that operating the engine  with a coolant/oil mix can result in internal engine damage. Replacing the intake manifold gasket should correct these leaks.

Body: A dirty throttle body may cause a lower than normal engine idle resulting in a stalling condition. A stalling condition may also result if an idle learn procedure is not performed if the battery goes dead or is disconnected.

The water pump may develop a coolant leak resulting in an engine overheating condition.


The fuel pump may fail causing engine to stall and not restart.

The upper intake manifold gasket and/or a PCV vacuum lines/hoses can develop vacuum leaks with age. This type of leak can result in a higher that normal or rough idle.

The oxygen sensor can fail causing Check Engine Light illumination and the engine to run rich (burn more fuel than normal).

The ignition coil housing may fail causing an engine misfire on one or more cylinders.

The ignition module or crankshaft position sensor may fail causing the engine to die and not restart. Diagnoses will be necessary to determine if the module or crank sensor is causing the no start condition.

You may be able to prevent transmission problems by servicing the transmission and inspecting the fluid every 30,000 miles. If the fluid is dark or burned then the transmission system should be completely flushed.

The spark plugs should be replaced every 30,000 miles and the spark plug boots should be checked for hot spots and cracks.

The Engine Control Module (ECM) can fail causing stalling, and engine and transmission drivability concerns.

A stalling issue may occur if the battery goes dead or is disconnected and the "idle learn" procedure is not performed. For more information on "relearning" the engine idle speed, please click here»

An engine oil leak may develop from the oil pump drive O-ring. This can often be confused with an intake manifold gasket leak. Careful inspection is required to determine the exact cause of the leak. Replacement of the failed 0-ring will commonly correct this concern.

Contaminated brake fluid can cause problems in the brake system and it should be flushed every 60,000 miles.